Behavioral architecture of the cortical sheet Rodney J. Douglas, Kevan A.C. Martin  Current Biology  Volume 22, Issue 24, Pages R1033-R1038 (December 2012) DOI: 10.1016/j.cub.2012.11.017 Copyright © 2012 Elsevier Ltd Terms and Conditions

Figure 1 Development of the forebrain in the mouse. Schematic representation of the embryo at about embryonic day E13, showing the dramatic enlargement and elaboration of the anterior neural tube (adapted from Puelles, 2000). Top, transverse aspect; bottom left, dorsal aspect; bottom right, medial aspect. Cyan: pallial, presumptive cortical components of the telencephalon hemispheres (TH). Magenta: subpallial presumptive basal ganglionic components (BG). Light brown: limbic cortices (lim cx) and limbic nuclei (lim nucl). Grey: diencephalon (dien) and more caudal brainstem. OB: olfactory bulb. OT: optic tract. Current Biology 2012 22, R1033-R1038DOI: (10.1016/j.cub.2012.11.017) Copyright © 2012 Elsevier Ltd Terms and Conditions

Figure 2 Adult human cortical sheet. Schematic representation of the flattened cortical sheet of the right cerebral hemisphere and some of its related structures (adapted from van Essen and Drury, 1997). Cyan: cortical sheet; relevant limbic structures shown schematically as light brown blobs. The central sulcus (red, CS) and inferior-central sulcus (red, ICS) divide the sheet in the coronal plane. The highly convoluted and approximately hemispherical cortex has been flattened by making a few relieving cuts to preserve as far as possible the true relative sizes and major spatial relationships of cortical areas. The temporal cortex is separated from the more medial cortex by the prominent lateral sulcus (black, LS). In three dimensions, parts of the temporal and orbital cortex and the limbic components fold back under the cortical plate so that the divided septum and hippocampus in fact form continuous ‘medial’ structures. Current Biology 2012 22, R1033-R1038DOI: (10.1016/j.cub.2012.11.017) Copyright © 2012 Elsevier Ltd Terms and Conditions

Figure 3 Functional organisation of cortical sheet. Schematic showing functional organization of cortical sheet of the right hemisphere and some of its related structures, Above: transverse section shows how the sheet folds in three dimensions, so that limbic nuclei, basal ganglia (gp, globus pallidus; caud/put, caudate and putamen), and hippocampus (hippo), come to occupy more ‘medial’ positions, interposed between the neocortex and the medial telencephalon and diencephalon beneath (not shown). Below: unfolded in plan view, the cortical sheet (cyan) is surrounded by limbic cortices (brown, e.g. cingulate cortex, insula) and their associated nuclei (red, e.g. septal nuclei, amygdala). The concept presented here is that the components of behavior are systematically distributed across this regular sheet. Around the central sulcus (thick red horizontal line) processing relates to the direct and immediate engagement of the agent with its environment. The more anterior cortex processes potential action repertoires, plans and goals that extend forward in time, whereas the more posterior cortex processes space, which extends progressively further from the agent (and so also further into future planning time). The temporal lobe encodes objective structures such as places, objects, and faces. This lobe is greatly enlarged in primates, including humans, and is intimately related to the declarative memory functions involving the hippocampus. The emotive subjective signals of the limbic cortices color/bias the processing of the evolving plans of the more medial areas. More lateral cortical areas are relatively isolated from these colorings and process alternative action sequences and spatial structure in a more semantically and syntactically objective manner. Dynamically evolving behaviors are represented schematically as graphical structures composed of ‘nodes’, the regions of active processing, and ‘edges’, which represent the axonal communication channels between active nodes. The channels act directly through cortico-cortical connections, or indirectly via thalamus and basal ganglia. Multiple behaviors may evolve simultaneously (green graph, see text), while the red graph represents the various functional relations of the behavior currently being executed. Current Biology 2012 22, R1033-R1038DOI: (10.1016/j.cub.2012.11.017) Copyright © 2012 Elsevier Ltd Terms and Conditions